Silicone coating cloth and air bag

ABSTRACT

The present invention provides a silicone coated fabric comprising a base woven fabric that is formed from a synthetic fiber weaving yarn that has a yarn size of from 100 to 270 dtex, and a weaving size expressed by a product calculated by multiplying the yarn size of a weaving yarn and a weave density (ends or picks/2.54 cm) of from 10,000 to 25,000 (dtex•ends (or picks)/2.54 cm) in both the warp direction and the weft direction, a silicone being applied to the woven fabric in an amount of from 5 to 25 g/m 2 , and having on one side a uniform silicone coating layer formeding part of the silicone mentioned above.  
     The silicone coated fabric of the present invention is a lightweight coated fabric that shows improved heat resistance, improved flexibility and an improved low coefficient of friction as well as particularly improved burning resistance. The fabric can therefore be used for producing lightweight and compactly storable airbags that suppress bursting starting from a burnt-through-hole, and that shorten a deployment time.

TECHNICAL FIELD

[0001] The present invention relates to a soft and lightweight siliconecoated fabric excellent in burning resistance and mechanical properties,a method of producing the same, and an airbag prepared therefrom.

BACKGROUND ART

[0002] An airbag provided to ensure the safety of an occupant in anautomobile at the time of collision is usually mounted in a small spacesuch as a steering wheel or an instrument panel in the form of a modulein which the airbag is stored in combination with an inflator. In orderfor a passenger car to be prepared against a side crash, an airbag hasrecently been provided in the form a side bag or side curtain. An airbagin such a varied form is also stored in a small space such as a sideportion of a car sheet or a roof/pillar portion. In order to ensureample occupant space in a car, without reducing it under suchcircumstances, it is required to make the stowed volume of the airbag assmall as possible and, further, to make the airbag system light.

[0003] In order to make the airbag compact and lightweight to meet therequirements, a base fabric for airbag that is a lightweight wovenfabric is required.

[0004] In order to make the stowed volume of an airbag small, a weavingyarn having a small yarn size has been used as a yarn for the wovenfabric. In order to make an airbag airtight, the type and amount of anelastomer to be applied to the base woven fabric have been adjusted. Forexample, the size of a yarn to be used for the woven fabric is decreasedfrom 940 dtex to 470 dtex. Moreover, the elastomer has been changed fromchloroprene to silicone, and the coating amount has been decreased, from90 to 120 g m², to from 40 to 60 g/m². A coated fabric prepared bycoating a base woven fabric having a yarn size of 470 dtex with asilicone resin is currently being used.

[0005] Recently, airbags have been required to be even more lightweightand compact. Accordingly, references such as WO 01/09416 disclose theuse of a weaving yarn having a smaller yarn size (from 67 to 250 dtex)for the purpose of making a woven fabric for an airbag more lightweight,and the use of a weaving yarn having a smaller size filament (singlefilament size of from 0.5 to 4.5 dtex) for the purpose of making theairbags compact or making the woven fabric give a soft feel.

[0006] On the other hand, in order to make the coated fabriclightweight, it is desired that the coating amount is decreased.However, when the coating amount of silicone is decreased, the burningspeed increases, and a problem, that the burning speed exceeds the upperlimit that FMVSS 302 reguration specifies, arises. For example, JapaneseUnexamined Patent Publication (Kokai) No. 7-300774 discloses theproduction of a coated fabric that passes the flame proofness test,which comprises coating a fabric with a mixture prepared by adding solidpowder of a substance such as acetylene black and Fe₂O₃ to silicone.However, the coated fabric is not lightweight, because the coatingdisclosed has a thickness from 5 to 20 μm. Moreover, when powder of asubstance such as acetylene black or Fe₂O₃ is added to a siliconecomposition in an amount of from 5 to 10 mass parts as a solidcomponent, the solid powder cannot be sufficiently fixed with silicone.As a result, the following problems arise: the operator or thesurroundings is contaminated with solid powder that drops off thecoating during handling; solid powder that scatters during sewing anairbag clogs the eye of a sewing needle, and the sewing machine must befrequently repaired. When a solid powder accumulates in the eye portionof a sewing needle and/or thread guides, there is a possibility that acritical problem takes place in the step of sewing with an industrialhigh speed sewing machine due to a variation in the tension of feeding asewing yarn. A variation in the tension of feeding a sewing yarndestroys the balance between the tension of a needle thread and that ofa bobbin thread, resulting in the formation of a grinning seam to varythe thickness of an airbag product. Moreover, the tension of the runningyarn is varied to damage the sewing yarn or to produce a yarn break. Asa result, a problem, that the reliability of the airbag deployabilitymight be impaired, arises.

[0007] Japanese Unexamined Patent Publication (Kokai) No. 2001-138849describes a lightweight coated fabric with excellent stowability that isprepared from a woven fabric formed from a yarn with a yarn size of from100 to 250 denier and coated with a silicone rubber in an amount of from5 to 35 g/m², and that can prevent a gas leak. However, the patentpublication discloses neither a sufficient suppression of burning speedwith a light silicone coating nor the design of a coated fabric that isa lightweight woven fabric and that has mechanical properties sufficientfor ensuring an inflating pressure resistance of the airbag.

[0008] Japanese Unexamined Patent Publication (Kokai) No. 5-319194discloses an attempt to improve the softness of an airbag by a procedureof applying a silicone to the base woven fabric. In the attempt, anairbag base fabric formed of a weaving yarn having a yarn size of from420 to 840 denier is impregnated with an amino-modified silicone as asoftening agent and a methylhydrogensilicone (0.11 to 0.49% by weight)as a water repellent to form an air permeable woven fabric layer. Thewoven fabric is further coated with a silicone elastomer to form an airimpermeable coating layer (35 to 65 g/m²). The patent publicationdescribes that an impact on a human body caused by the deployment of theairbag can be made small, as a result. However, when a base woven fabricformed from a yarn with a yarn size as small as 270 dtex or less andhaving a lightweight coating of 25 g/m² or less is prepared by the abovemethod in order to aim at a lightweight airbag, the coated base wovenfabric cannot pass the FMSS 302 burning test.

[0009] Japanese Unexamined Patent Publication (Kokai) No. 11-1876discloses an embodiment in which the pressure of an airbag is maintainedby coating a hollow woven base fabric formed of a weaving yarn having ayarn size of 420 denier with a double-layered silicone elastomer. Thepatent publication describes as follows. The first layer contains ahydrogensilicone that is a molecular chain extender and a silicone witha high breaking point elongation caused by a reinforcing filler of fumedsilica. The second layer contains a silicone having a high tear strengthand crosslinked with a vinylsilicone having three or more functionalgroups. The coating in a coating amount of from 60 to 220 g/m² acts tomaintain the pressure. However, the patent publication does not disclosethe design of a coated fabric that can maintain the pressure of anairbag while it makes the airbag lightweight.

[0010] During the deployment of an airbag, hot particles derived fromthe burnt residue of a gas-generant in the inflator sometimes form amelt hole, termed a burnt-through-hole, in the bag. When the heatcapacity of an airbag fabric that is made from small yarn size syntheticfiber is small, the possibility of forming a melt hole becomes high.Accordingly, means for preventing the bursting of an airbag, that startsfrom the melt hole, is required. Moreover, ideally, an airbag mustdeploy immediately at the time of a collision to restrain an occupant.Therefore, an airbag that shows a short deployment time is alsorequired.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1(A) shows an explanatory view for illustrating how to foldan airbag in the method of evaluating the compactness of the airbag.

[0012]FIG. 1(B) is an explanatory view for illustrating the state of anintermediately folded airbag.

[0013]FIG. 2 is an explanatory view showing a method of measuring thefolded thickness of an airbag.

[0014]FIG. 3 shows scanning electron microscopic (SEM) photograph of across-section showing an overlapped portion of weaving yarns in thesilicone coated woven fabric in Comparative Example 74, and a chartexhibiting an XMA (Si) elemental comparative distribution in the crosssection. The X-axis (vertical direction) in the chart indicates adirection from the front surface of the woven fabric to the backsurface, and the Y-axis (transverse direction) shows a count number ofthe Si signal.

[0015]FIG. 4 shows scanning electron microscopic (SEM) photograph of across-section of an overlapped portion of weaving yarns in the siliconecoated woven fabric in Example 73, and a chart exhibiting an XMA-Sielement (Si) distribution in the cross section.

[0016]FIG. 5 is scanning electron microscopic photograph (SEM)perspectively showing a cross section and a surface shape of the coatingsurface of the silicone coated fabric in Example 73.

DISCLOSURE OF THE INVENTION

[0017] An object of the present invention is to provide aburning-resistant silicone coated fabric that is excellent in lightness,softness and compactness, and that can pass the FMVSS 302 test.

[0018] A more specific object of the present invention is to provide asilicone coated fabric suitable for the production of an airbag that hasthe mechanical property of resisting an inflating pressure during itsdeployment, that suppresses bursting caused by a burnt-through-holeduring the deployment, that shows excellent restraining properties dueto a shortened deployment time, and that hardly injures an occupant.

[0019] The present inventors have found that when a silicone coatinghaving a specific coating structure is formed on a soft, dense wovenbase fabric formed from a weaving yarn having a yarn size of 270 dtex orless, a silicone coated fabric having burning inhibition properties(passing the FMVSS 302 burning test) on excellent level even though thefabric is a lightweight coated one has a small amount of coating, andcapable of giving a lightweight airbag that suppresses bursting causedby a burnt-through-hole can be obtained. The silicone coated fabric is alightweight coated one having a small amount of silicone coating, andensures air impermeability under high pressure while the coated fabricparticularly has the softness of the fabric and improved frictionalproperties. Accordingly, the present inventors have found that a compactairbag that shortens a deployment time can be manufactured from thesilicone coated fabric; they have thus achieved the present invention.

[0020] The present invention provides a silicone coated fabric

[0021] comprising a base woven fabric that is formed from a syntheticfiber weaving yarn having a yarn size of from 100 to 270 dtex, and “awoven yarns size parameter” expressed by a product calculated bymultiplying the yarn size of the weaving yarn and the weave density(ends (or picks)/2.54 cm) of from 10,000 to 25,000 (dtex•ends (orpicks)/2.54 cm) in both the warp direction and the weft direction,silicone being applied to the woven fabric in an amount of from 5 to 25g/m², and

[0022] showing a maximum burning speed of from 70 to 150 kW/m² in theradiation burning test using a cone calorimeter.

[0023] The silicone coated fabric of the present invention can beproduced by a method comprising coating a woven fabric that is formedfrom a synthetic fiber weaving yarn having a yarn size of from 100 to270 dtex, and “a woven yarns size parameter” determined by a productcalculated by multiplying the yarn size and the weave density (ends (orpicks)/2.54 cm) of from 10,000 to 25,000 (dtex•ends (or picks)/2.54 cm)in both the warp direction and the weft direction with silicone in anamount of from 5 to 25 g/m² by a combination of the two types ofapplications mentioned in (1) and (2) below, and then crosslinking thesilicone coating:

[0024] (1) applying to the woven fabric a dope composed of a siliconecomposition in an amount of from 1 to 21 g/m² as a solid component; and

[0025] (2) coating the woven fabric with a liquid silicone compositionin an amount of from 4 to 24 g/m².

[0026] The silicone coated fabric of the present invention will beexplained below in detail.

[0027] <Texture of Base Woven Fabric>

[0028] In the bag formation of a lightweight airbag, the mass per unitarea of a coated fabric as a bag-forming material is required to besmall.

[0029] The yarn sizes of a warp and a weft that form the base wovenfabric of the coated fabric in the present invention are each from 100to 270 dtex, preferably from 110 to 250 dtex. The yarn size hereindesignates a total size of single filaments in a weaving yarn, namely,the warp (or weft) of a weaving yarn that forms the woven fabric(identical to a yarn). The yarn that forms the warp or weft may also bea twisted yarn, a doubled yarn or a collected yarn of a plurality ofyarns. That is, the base woven fabric is a woven one prepared by weavinga weaving yarn having a yarn size (in the above sense) of 270 dtex orless.

[0030] Furthermore, the base woven fabric in the present invention isformed from a weaving yarn having “a woven yarn size parameter“expressed by a product calculated by multiplying the total yarn size ofthe weaving yarn and the weave density (ends (or picks)/2.54 cm) of from10,000 to 25,000 (dtex•ends (or picks)/2.54 cm), preferably from 12,000to 20,000 (dtex•ends (or picks)/2.54 cm), more preferably from 13,000 to19,000 (dtex•ends/2.54 cm) in both the warp direction and the weftdirection. The woven fabric formed from a weaving yarn with a small yarnsize in the above range becomes a lightweight fabric composed of a highdensity woven fabric.

[0031] <Burning Speed of Coated Fabric>

[0032] When the coating amount of a silicone for a coated fabric to beprepared is decreased, the decrease in the amount of the silicone tobecome a burning inhibitor for the synthetic fiber that is a combustiblesubstance increases the burning speed. As the burning speed increases,it is observed that the burning inhibition behavior tends to becomeunstable.

[0033] The silicone coated fabric of the invention has a siliconecoating on the base woven fabric in an amount of from 5 to 25 g/m²,preferably from 7 to 18 g/m². Moreover, the coated fabric shows amaximum burning speed of from 70 to 150 kW/m², preferably from 100 to130 kW/m² in a radiation burning test using a cone calorimeter. When themaximum burning speed is lower, the silicone coated fabric can pass ahorizontal burning evaluation such as the FMVSS 302 burning evaluationmore easily, and the spread of fabric burning is inhibited more even ifhot particles derived from an inflator gas generant residue melt thesilicone coated fabric. Thus, the following phenomenon never takes placein the airbag for which the coated fabric of the present invention isused: a burnt-through-hole is formed therein, and the hole becomes astarting point and is developed to burst the airbag.

[0034] In order to obtain a lightweight airbag for which a base wovenfabric formed from a synthetic fiber is used, a base woven fabric formedfrom a weaving yarn having a small yarn size is used. The heat capacityper unit area of the woven fabric then decreases. Hot particles areusually observed as ashes sticking to the inside of the airbagsubsequent to deployment so that the synthetic fiber is melted. As aresult, a melt-cut through hole (burnt-through-hole) is sometimesformed. When the metsuke (basis of weight of fabric) of the woven fabricis made smaller, the size of the burnt-through-hole tends to increase. Atrace of a burnt-through-hole is sometimes observed in the brokenportion of a burst airbag, and the hole is sometimes observed to havebecome a starting point of the burst. On the other hand, although asilicone does not melt, it burns at high temperature. As a result, aburnt-through-hole is similarly formed in an airbag formed from aconventional lightweight silicone coated fabric, and it sometimesbecomes the starting point of burst. The silicone coated fabricaccording to the present invention suppresses the occurrences of aburnt-through-hole by a silicone coating that imparts a slow radiationburning speed to the fabric.

[0035] The cone calorimeter method (ADTM E 1354, ISO 5660) is aradiation burning method using a cone heater, and is a method used forevaluating the flame proofness of resin molded articles or the like. Inthe method, a sample is burnt under predetermined conditions with aradiant heat generated by a cone heater. The method is thereforesuitable for evaluating a burning behavior with excellentreproducibility. The burning speed measurement test method with a conecalorimeter will be described later. In the present invention, thebending of a fabric sample caused by thermal deformation is suppressedby placing the sample on a specific screen, and the burning heatgeneration behavior is measured so that a maximum burning speed isobtained.

[0036] The silicone coated fabric of the present invention shows thefollowing properties in the FMVSS 302 burning test: a) the fire goes outwithin a burning time of 60 sec and with a burning distance 50 mm orless; alternatively, b) the fabric sample burns at a rate of 80 mm/minor less at a burnt distance (the longest distance being 254 mm). Theburning evaluation herein is made on 10 or more silicone coated fabricsamples (n≧10) in each of the warp, weft and bias directions, and theevaluation is expressed by the maximum value. First, a sample that fallsinto the category a) shows a burning distance, which is a distance froma measurement-starting point 38 mm apart from an end that catches fireto a point where the fire goes out, of 50 mm or less, and a burning timeof 60 sec or less, and is judged to be self-extinguishing. Next, asample that falls into the category b) is one that does not fall intothe category a). The sample shows a burning speed, which is calculatedfrom a burning time consumed until the fire goes out at the burningdistance, of 80 mm/min, or a burning speed, which is calculated from atime consumed when the sample burns from the measurement-starting pointto a point 254 mm apart therefrom, of 80 mm/min or less. The sample isjudged to have slow combustibility.

[0037] When the coating amount of the silicone composition of aconventional silicone coated fabric is decreased, the coated fabric hasnot gained complete acceptance by the FMVSS 302 burning test. That is,an unstable burning inhibition behavior as explained below has beenobserved. A burning flame becomes large during burning, and cracks areformed on an incinerated coating of the silicone so that burning flamesbelch out, resulting in flame spreading. As a result, the followingproblems arise. The burning time and burning distance of test samplesincrease, and the variation of such value of evaluation increases;samples that deviate from the category of self-extinguishing sometimesappear, or samples that show a burning speed exceeding the requiredupper limit of 102 mm/min sometimes appear. The coated fabric of thepresent invention shows a decreased magnitude of a burning flame due tothe suppression of the maximum burning speed, so that it is suppressedburning speed in a horizontal burning evaluation due to thestabilization of a burning inhibition effect. As a result, even when thesamples are repeatedly evaluated according to the FMVSS 302 burningtest, they stably gain the evaluation of self-extinguishing or delayedburning to a high degree.

[0038] <Mechanical Properties of Coated Fabric>

[0039] An airbag is required to resist a gas pressure during deploymentand an internal pressure rises while restraining the occupant. In orderfor a lightweight airbag to have a pressure resistance at an ordinarydriver's seat, the airbag is required to have specific mechanicalproperties.

[0040] The silicone coated fabric of the present invention shows theratio of a tear strength (single tongue method) to a weaving yarnstrength of from 8 to 15, preferably from 9 to 13. The ratio relates toa number of cohering weaving filaments that cohere in the tear-formingregion (del) at a tear tip to resist a tear force. That is, the ratio isa tear cohesion ratio. When the tear cohesion ratio is 8 or more, thecohesion process of the filaments mildly absorbs energy in such aportion to which a tearing load is sharply applied during deployment asa bolt hole where the airbag is attached and fixed to a module. As aresult, the airbag is not damaged. On the other hand, when the tearcohesion ratio is excessively high, the tensile opening in the seam ofthe bag increases, and a seam leak burst is produced by the inflatorgas. When the tear cohesion ratio is 15 or less, the hot burst of thebag can be suppressed.

[0041] The silicone coated fabric of the invention shows a biaxialtensile breaking strength of from 4,000 to 8,000 N/20 cm, preferablyfrom 4,500 to 7,000 N/20 cm. When the breaking strength in a biaxialtensile test is 4,000 N/20 cm or more, the airbag base fabric is neverdamaged. When the biaxial tensile breaking strength increases more, theinflating pressure resistance also increases further. However, there isa restriction on the biaxial tensile breaking strength of a lightweightairbag due to the yarn size and the weave density.

[0042] The biaxial tensile test is a tensile breaking test conducted byholding a coated fabric sample in the warp and weft directions andsimultaneously drawing the sample in both directions. When an airbag isdeployed to restrain an occupant, the airbag must resist the inflatingpressure as a pressure vessel. The stress applied to the coated fabricis generated as a biaxial stress. In contrast to the tension testwherein there is a degree of freedom in the counter axis direction and acontraction factor is present in combination with the tensile factor,the biaxial tensile test represents the actual mechanical properties ofthe airbag during its deployment.

[0043] <Structure of the Silicone Coating>

[0044] The silicone coated fabric of the present invention shows aspecific silicone distribution in a cross section of the fabric. Thatis, when a cross section of the silicone coated fabric is observed bySEM, the Si element distribution determined by SEM/XMA has a maximumpeak and the other peaks having from {fraction (1/20)} to ⅔ of the peakcount in a central 50% portion where a warp and a weft are overlapped(interlaced) by weaving on the front and back sides. In the presentinvention, a silicone applied to a base woven fabric is thinly anduniformly distributed among constituent filaments of weaving yarns ofthe woven fabric, and part of the silicone is segregated and distributedover the woven fabric surface, etc. Moreover, a silicone forms a thincoating layer on one side of the woven fabric surfaces. When the crosssection of the silicone coated fabric of the invention is observed bySEM, a cross-sectional structure in which a silicone coating layer isformed on the surface of the woven fabric cross section is observed(refer to FIG. 5 and FIG. 6). Furthermore, the elemental distributionanalysis of Si carried out by SEM/XMA gives the following results: amaximum count of Si is obtained in a portion corresponding to thesilicone thin coating layer thus formed; a very small amount of Si isdistributed among filaments; segregated silicone exists on the wovenfabric surface where no silicone coating layer exists, namely, the backside of the coated woven fabric (refer to FIG. 5 and FIG. 6), etc.

[0045] It is in a portion where a warp and a weft are overlapped(interlaced) by weaving on the front and back sides in the cross sectionof the woven fabric that the distribution structure of the siliconeshown by elemental analysis of Si characteristically appears. It isnecessary in the present invention that the Si distribution have such astructure in the central portion of overlapped weaving yarns of a warpand a weft of the base woven fabric. Analysis of the Si distribution iscarried out by preparing a cross-sectional sample of the coated wovenfabric with the cross section including a center where a warp and a weftare overlapped by weaving on the front and back sides, and carrying outelemental analysis of Si by SEM/XMA. Each of the weaving structuralrepeating units of the weaving yarns is observed, and the distributionanalysis is carried out at a site situated in a range along a repeatingunit from an overlapped center of the weaving yarns to 50% of therepeating unit length. A Si distribution amount (Y coordinate) isplotted against a distance (X coordinate) in the direction from thefront surface (coated surface) to the back surface of the woven fabric.Then, a maximum count peak is observed at a position corresponding tothe silicone thin coating layer. Moreover, there is a Si distributionamong filaments in a very small amount.

[0046] Furthermore, a peak of segregated silicone can be observed on thesurface of the woven fabric substantially free of the silicone thincoating layer, namely, the back surface of the coating; in some cases, aplurality of segregation peaks including a peak present in the midwaybetween the front and back sides of the woven fabric are observed.

[0047] In the present invention, the peak height of the elementaldistribution of Si of the segregated silicone is from {fraction (1/20)}to ⅔, preferably from {fraction (1/10)} to ½ of the maximum peak heightthereof in the silicone coating portion. When the peak height ratio is{fraction (1/20)} or less, contribution of a silicone other than thecoating silicone to the inhibition of burning is insignificant, andspreading of the burning of the synthetic weaving yarns cannot beinhibited during the formation of a burnt-through-hole. On the otherhand, when the peak ratio is ⅔ or more, a silicone coating with a largeweight is formed on both sides of the woven fabric. Alternatively, anonuniform silicone coating is formed even when the coating islightweight. As a result, the burning inhibition behavior becomesunstabilized, and the air impermeability under high pressure cannot beensured.

[0048] <Deployment of Airbag and Deployment Friction of the Bag of theAirbag>

[0049] Ideally, an airbag should immediately deploy in a crash torestrain an occupant. An airbag is therefore required to completedeployment in a short period of time to be ready for restraining anoccupant.

[0050] A lightweight airbag has the potential that the deployment timeis short because the energy for transferring the center of gravity issmall. In order to utilize the advantage, it is first desired to reducethe resistance produced when fabrics forming the bag and being in acompactly folded state spread and expand while rubbing each other at thetime of deployment.

[0051] The silicone coated fabric of the present invention shows acoefficient of friction (MIU), measured by KES, of from 0.05 to 0.3 inthe warp and weft directions on the front and back sides thereof. Whenthe coated fabric is made to have a coefficient of friction (MIU) in theabove range, the low coefficient of friction contributes to the highspeed deployment of an airbag. Moreover, the present invention canprovide an airbag that gives a soft touch to an occupant and that causesno abrasion of the occupant during its deployment.

[0052] A measurement by KES (Kawabata's evaluation system for fabric)herein refers to a method of measuring basic dynamic characteristics ofa fabric for the purpose of digitizing the feeling, namely, the touch ofa fabric that a human body percepts, and is defined in the reference:The Standardization and Analysis of Hand Evaluation, 2^(nd) ed., S.Kawabata, the Textile Machinery Society of Japan, July 1980.

[0053] There are several measurements by KES that indicate variousmechanical properties of a fabric. The measurement by KES for evaluatingthe frictional properties of a fabric uses a friction probe described inthe above reference, and a sample fabric, horizontally held with apredetermined tension on a table, is moved in the warp and weftdirections, whereby the coefficient of friction (MIU) can be measuredfrom a tension, i.e, frictional force, imported to the friction probe,which exerts a vertical load on the sample fabric. The surface slidingstate of the coated fabrics of the invention can be evaluated bymeasuring the coefficient of friction by KES. In the present invention,in order to clarify a frictional resistance between two coated fabrics,a coated fabric sample is affixed to the surface of a friction probedefined by KES, and measurements are made. The measurement conditionswill be described in detail later.

[0054] When the coefficient of friction of a silicone coated fabric isin the above range, damage to the keratin of a human skin is reduced,and the possibility of injuring an occupant with the airbag can bedecreased even when the human body is contacted with the airbag duringits deployment and spreading or a human body is forced into a deployedairbag.

[0055] <High Speed Deployment of Airbag and High Pressure AirImpermeability of the Bag Body>

[0056] The silicone coated fabric of the present invention shows an airpermeability of 1.0 cm³/cm²/sec or less, preferably 0.1 cm³/cm²/sec orless at a pressure of 300 kPa. The deployment gas pressure of an airbagmomentarily reaches a large magnitude exceeding 200 kPa. The siliconecoated fabric of the present invention maintains air impermeability evenunder such high pressure. As a result, the fabric can utilize the energygenerated by an inflator gas with sufficient effectiveness to deploy theairbag at high speed. During the instantaneous deployment of an airbagwith an inflator gas at high pressure, the airbag maintains airimpermeability. Even after maintaining a pressure of 50 kPa for 10 secafter the deployment, the airbag holds the pressure well and holds theexpanded state. The airbag therefore achieves the effect of protectingan occupant when an automobile rolls over.

[0057] <Single Filament Size of a Weaving Yarn Forming the Base WovenFabric>

[0058] The size of a constituent single filament of a weaving yarn thatforms the base woven fabric of the silicone coated fabric in the presentinvention is from 0.5 to 4.5 dtex, preferably from 1.0 to 3.5 dtex. Abase woven fabric having a small single filament size has advantages asexplained below. First, an airbag having a compact foldability can beobtained because the bending rigidity of the coated fabric is decreased.Second, the single filament size contributes towards shortening thedeployment time for the following reasons. Because a coated fabric wovenfrom yarns composed of small sized filaments exhibits small bendinghysteresis, the coated fabric is hardly creased. As a result, the airbagin a compactly folded state can be easily expanded and deployed. Third,the use of thin single filaments forms a woven fabric having nointervening pores at the meai portion (intervening portion betweenneighboring woven yarns) because the single filaments of the weavingyarn cover the meai portions of the front and back side of the fabric.Consequently, a lightweight uniformly coated fabric having a relativelysmooth woven fabric surface can be prepared. The coated fabric havingsmooth and fine recesses and protrusions shows a decreased frictionresistance, and contributes toward shortening the deployment time.Fourth, the form of a uniform silicone coating decreases the formationof coating cracks during burning, and burning is inhibited. Fifth, for awoven fabric having no macroscopic recesses and protrusions such as meaipores, a microscopically relatively uniform coating is formed on thesurface layer of groups of fine single filaments. As a result, thecoating suffers no microscopic destruction when the fabric is deformedunder high pressure. The fine single filaments thus contribute towardsuppressing gas leakage. Sixth, silicone allowed to penetrate amongsingle filaments having a small size promotes the effect of inhibitingburning to increase the effect of suppressing the spread of burn-throughburning.

[0059] <Constituent Fiber Material of the Woven Fabric and Weaving theBase Woven Fabric>

[0060] There is no specific limitation on the constituent synthetic yarnof a base woven fabric for the silicone coated fabric in the presentinvention. However, polyhexamethylene adipamide and polytetramethyleneadipamide that have a high melting point and a large heat capacity arepreferred. Moreover, a yarn mainly containing polyhexamethyleneadipamide is also preferably used. Of these yarns, the following yarnshaving a melting point of 215° C. or more are particularly preferred inview of the heat resistance: a polyhexamethylene adipamide (hereinaftermerely referred to as nylon 66) yarn, a nylon 66 copolymer (nylon 66/6,nylon 66/6I, nylon 66/610) yarn, or a nylon 66 yarn obtained by blendingnylon-based polymers (nylon 6, nylon 610, etc.). Moreover, these yarnsmay also contain various additives conventionally used for the purposeof improving the productivity in the production step and spinning stepof the yarns and the properties thereof. For example, the yarns maycontain thermal stabilizers, antioxidants, light stabilizers, smoothingagents, antistatics, plasticizers, viscosity improver, pigments, flameretardants and the like.

[0061] The tensile strength of a yarn forming the silicone coated fabricof the present invention is preferably 5.7 cN/dtex or more, morepreferably 6.2 cN/dtex or more, particularly preferably from 6.2 to 11cN/dtex. A combination of a tensile strength of 5.7 cN/dtex or more withthe weave density of the woven fabric can ensure the strength of thecoated fabric.

[0062] The base woven fabric used for the silicone coated fabric of theinvention is satisfactory as long as it is a woven fabric having atexture such as a plain weave, a rip-stop weave and a bascket weave. Thefabric can be woven on a conventional loom such as an air-jet loom, awater-jet loom, a lapier loom and a multi-phase weaving machine. Thereis no specific limitation on the method of weaving the base wovenfabric.

[0063] <Method of Applying a Silicone Coating>

[0064] The silicone coated fabric of the invention is prepared byapplying the coating steps (1) and (2) described below to a given basewoven fabric to apply a silicone to the base woven fabric in a totalcoating amount of from 5 to 25 g/m², and crosslinking the appliedsilicone.

[0065] (1) A coating step of applying a dope composed of a siliconecomposition in an amount of from 1 to 21 g/m² as a solid component.

[0066] (2) A coating step of coating the woven fabric with a liquidsilicone composition in an amount of from 4 to 24 g/m².

[0067] That is, the silicone coating of the invention is formed with twotypes of coatings applied to the base woven fabric by the separatecoating steps. The two coatings have functions different from eachother. The coating step (1) is a step of applying a silicone dope havinga relatively low viscosity (hereinafter referred to as dopeapplication). On the other hand, the coating step (2) is a step ofapplying a silicone having a relatively high molecular weight to oneside of the base woven fabric to form a coating layer adhering to thebase woven fabric surface (hereinafter the step being referred to asthin layer coating).

[0068] A dope in the coating step (1) is a diluted solution of asilicone having a low viscosity of preferably from 0.1 to 5 Pa•s (at 25°C.,the temperature being the same hereinafter).

[0069] The silicone composition used in the dope application principallycomprises an addition crosslinking type silicone. For example, thesilicone composition preferably comprises (a) an organopolysiloxanehaving alkenyl groups (including vinyl groups) at the molecular chainends, (b) an organosiloxane having three or more hydrogen atoms attachedto Si atoms, namely, three or more Si—H functional groups, (a) acatalyst that accelerates addition of Si—H functional groups toaliphatic multiple bonds, and (d) an organosilicon compound suitable asan adhesion aid of a silicone to a synthetic fiber polymer.

[0070] In particular, the principal agent silicone (a) has a viscosityof preferably from 0.1 to 10 Pa•s. An elastomer obtained by vulcanizing,namely, crosslinking a low viscosity silicone has a small molecularweight between the crosslinkings. As a result, the elastomer has a highcrosslinking density. A silicone having a high crosslinking densityshows about a half burning speed. The silicone coated fabric thereforeburns with a smaller burning flame to exhibits a slow burning speed.

[0071] The physical properties of the elastomer formed from the siliconecomposition can be measured by the following procedure. The liquidsilicone composition is vacuum defoamed in the absence of solvent, andthe composition is cross linked by hot press molding (170° C.×5 min) togive tensile test pieces (JIS K-6251/dumbbell No. 3). Measurements aremade on the test pieces. The physical properties of the elastomer of thesilicone composition used in applying a dope are desirably as follows: atensile strength of from 0.5 to 4 N/mm²; and a tensile breakingelongation of from 20 to 200%.

[0072] When the viscosity of the silicone composition having a lowviscosity is in the above range, the silicone composition can be used asa dope without dilution. The dope is usually a diluted solution (withorganic solvent) of a silicone having a low viscosity or an aqueousemulsion of a silicone having a low viscosity. The aqueous emulsion canbe made to have a solid component content of from 1 to 60% by weight.

[0073] The coating method can be suitably selected from dip coating,knife coating, fountain coating, roll coating and the like. A methodsuch as dip coating by which the silicone is allowed to penetrate intothe base woven fabric texture is preferred. The viscosity of the dope issuitably adjusted to the above range in accordance with a coating methodapplied.

[0074] When a silicone dope is applied by a procedure as explainedabove, the silicone is distributed over the entire texture of the basewoven fabric, and is partially segregated on the surface thereof in thecourse of removing the water or solvent.

[0075] It is important that a low molecular weight silicone adequatelypenetrate into even single filaments of a yarn of a synthetic fiberforming the base woven fabric and distributed. The dope is preferablyapplied to the base woven fabric by dip coating or the like so that thedope sufficiently penetrates into the constituent fiber filaments of thewoven fabric. When the silicone is applied in such a manner, asexplained above, that the silicone is contacted with and distributed tosubstantially the entire synthetic fiber filaments forming the basewoven fabric, the burning speed is suppressed. Moreover, when a siliconeis present on the base woven fabric only slightly, damage to the skin issignificantly decreased. Accordingly, even the base woven fabric surfaceto which the dope is applied shows a decreased tendency toward damagingthe skin.

[0076] The coating amount of the silicone composition used in applying adope is from 1 to 21 g/m² as a solid component, preferably from 3 to 15g/m². When the coating amount is in the above range, the lightness andflame proofness of the coated fabric subsequent to two types of coatingare satisfied.

[0077] The coating in the coating step (2) is a step of forming auniformly thin coating layer which step is applied to one side of a basewoven fabric to manifest on the base woven fabric the recessed andprotruded shapes of ridges formed by the weaving yarns. The coatinglayer thus formed forms a firm incinerated film, when the silicone isburnt, to suppress the blowout of a burning gas and inhibit the spreadof burning. The coating layer therefore has a function of shortening aburning distance. A coated fabric having only an applied dope shows arelatively large radiation burning speed, whereas a coated fabric with acomposite of a dope and a thin coating layer shows a delayed radiationburning speed and a shortened horizontal burning distance. Moreover, therecessed and protruded shapes of the coating reduce the tackiness of asilicone, and improve the friction behavior to shorten the deploymenttime of the airbag.

[0078] The liquid silicone composition applied in the coating step (2)has a viscosity of from 5 to 1,000 Pa•s, preferably from 10 to 500 Pa•s.The liquid silicone composition is desirably applied to the base wovenfabric by a non-solvent procedure without diluting with an organicsolvent. A liquid silicone having a viscosity in the above range doesnot penetrate into the texture of the base woven fabric, and is likelyto accumulate on the surface. It is important that the coating resindoes not penetrate into the texture of the base woven fabric so that theresin is present on the woven fabric surface as much as possible. Thesilicone coated fabric can thus be modified to pass the FMVSS 302burning test. That is, when the silicone coating on one side is uniformand the minimum coating thickness is adequately ensured, formation of acoating that brings about the following phenomenon can be avoided, andthe burning distance can be stably shortened: the coating layer isbroken from a thinner portion of the resin during burning, and a burninggas is blown out. When the liquid silicone composition has a viscosityof 1,000 Pa•s or less, the resin flows stably during coating, and thecoating shows excellent adhesion to the applied silicone dope. Theliquid silicone composition used for coating is applied in an amount offrom 4 to 24 g/m², preferably from 5 to 15 g/m² as a solid component.When the coating amount is in the above range, the silicone coatedfabric prepared by applying two types of coatings has satisfactorylightness and flame proofness.

[0079] The liquid silicone composition used in the thin coating thewoven fabric preferably comprises, for example, (A) anorganopolysiloxane having alkenyl groups (including vinyl groups) mainlyat molecular ends, (B) an organopolysiloxane having 3 or more hydrogenatoms attached to Si, namely, 3 or more Si—H functional groups in themolecule, (C) a catalyst that accelerates addition of Si—H functionalgroups to aliphatic multiple bonds, (D) an organosiloxane compoundsuitable as an adhesion aid for a silicone resin and a synthetic fiberpolymer, and (E) a reinforcing filler such as silica. In particular, theprincipal agent silicone (A) has a viscosity of from 1 to 1,000 Pa•s,preferably from 2 to 100 Pa•s. In order for the silicone coating to havea necessary mechanical strength, the above viscosity, namely molecularweight, is required. Moreover, the toughness of the crosslinked coatingis preferably increased with a silica filler, etc. Furthermore, theviscosity of the coating liquid is preferably increased to from 5 to1,000 Pa•s, more preferably from 10 to 500 Pa•s.

[0080] The physical properties of an elastomer of the siliconecomposition used in thin layer coating the base woven fabric aredesirably as follows: a tensile strength of from 2 to 10 N/mm²; and atensile elongation at break of from 150 to 600%. The tensile propertiesare obtained by a tensile test of a molded piece explained above.

[0081] Contact pressing type coating is used as the coating procedure.Coating procedures such as various commonly used knife coatingprocedures, roll coating, reverse coating, and the like can be employed.When a coating procedure (gap procedure) in which a gap is providedbetween a base woven fabric and a coating head is practiced, not onlythe restriction of the coating amount is difficult but also a coatingsurface in which recesses and protrusions of ridges of a woven yarntexture are manifested cannot be obtained. Contact pressing conditionsin knife coating are as follows: a linear pressure is preferably from 1to 500 kgf/m, more preferably from 20 to 300 kgf/m. When the linearpressure is higher, a coating in a smaller amount can be obtained.Moreover, a coating surface that conforms contours of the recessed andprotruded shape of ridges of woven texture can be obtained. In thepresent invention, the recesses and protrusions of a woven fabric aremade flat at the moment when the coating head such as a knife edgeconducts coating, and the coated film is formed with a uniformthickness. Because the recesses and protrusions of the woven fabricsurface are recovered when the coating head passes, a coating face thattraces the recessed and protruded shape of the woven fabric surface isformed. The linear pressure conditions can be suitably determined inaccordance with the viscosity of the dope or the liquid siliconecomposition, namely, the viscosity of the liquid silicone composition,and the coating head shape. The substantial contact pressure is affectedby the contacting area of the coating head on the fabric. For example, aknife having an edge thickness from about 4 mm to about 10 μm should besuitably selected. A knife having a smaller thickness shows a highersubstantial contact pressure; therefore, a recessed and protruded shapecan be formed by coating the fabric with a smaller amount of a coatingcomposition. The shape of the coating knife may be semicircular,rectangular or recessed at the tip. The radius of the semicircular shapeshould be from 0.005 to 2 mm. The radius of the rectangular shape shouldbe from 1.0 mm or less. The coating speed is preferably from 1 to 100m/min, more preferably from 10 to 50 m/min. The coating layer surfacethat traces the recesses and protrusions of the surface of the basewoven fabric does not have the tackiness that a conventional siliconecoating surface has, and decreases the friction resistance. The coatingsurface therefore contributes toward shortening the deployment time ofthe airbag.

[0082] Crosslinking treatment is conducted after each of the siliconeapplications. Alternatively, crosslinking treatment is carried outcollectively after the coatings. Crosslinking treatment may be carriedout in accordance with the crosslinking system of the elastomer. Forexample, when an addition type silicone elastomer is going to becrosslinked by thermally inactivating a catalyst inhibitor for thecrosslinking reaction, heat treatment should be conducted attemperatures of from about 150 to 230° C. for about 0.1 to 5 minutes.

[0083] A coupling agent that improves adhesion to synthetic fibers ispreferably added to any of the silicone compositions used in the presentinvention. For example, an alkoxysilane having an epoxy group, or thelike is preferably added in an amount of from 1 to 15% by weight.Moreover, it is preferred that a crosslinkable silicone having a Si—Hbond is excessively added, so that a Si—H/vinyl (alkenyl) functionalgroup ratio is in a range of from 5 to 200. Such an improvement ofadhesiveness contributes to the improvement of the tear strength.

[0084] Furthermore, known thickeners, flame-resistant agents,stabilizing agents, and the like may be added to any of the abovesilicone compositions used in the present invention as long as theeffects of the present invention are not impaired. During the addition,an insoluble solid additive such as a pigment is added to the siliconecomposition in an amount of preferably less than 5% by weight, morepreferably less than 1% by weight. It is most preferred that pigmentsand the like are not added.

EMBODIMENTS OF THE INVENTION

[0085] The present invention will be concretely explained below bymaking reference to examples.

[0086] In the examples, “parts” designate parts by weight. The methodsof evaluating a silicone coated fabric are as follows.

[0087] (1) Weave density

[0088] The weave density is measured according to JIS L-1096 8.6.1.

[0089] (2) Total Weight of Coating

[0090] A sample having an area (A) of about 0.3 m×0.3 m is taken from asilicone coated fabric, weighed accurately, and dried at 105° C. for 2hours or more. The sample is subsequently degreased withdichloromethane, and dried. The sample is then dissolved in 200 g offormic acid (90%) at room temperature for 3 hours. The insolublecomponent is separated by filtering with a glass sintered filter(manufactured by Vidrex Co., Ltd., trade name of Glass Filter 17G-3),adequately washed with formic acid, washed with water, and dried at 105°C. for 2 hours. The dried weight (M) of the insoluble component ismeasured. The total coating weight (g/m²) is obtained by dividing theformic acid-insoluble component (M) by the area (A) of the coated fabricsample.

[0091] (3) Maximum Burning Speed with a Cone Calorimeter

[0092] A silicone coated fabric is adjusted to be in a standard stateaccording to JIS L 0105, and a rectangular sample, 94×94 mm, is takentherefrom. The sample is placed on the table of measuring equipment withthe coated layer side up. A screen of Nichrome wire with 0.25 mmφ,100×100 mm, with a 10 mm-mesh is placed on the sample, and set. Using acone calorimeter (trade name of III-C3, manufactured by Toyo SeikiSeisaku-sho, Ltd.) according to ASTM E 1354, ISO 5660, the sample isheated with a cone heater in air atmosphere. The cone heater is providedso that the radiant calorie becomes 50 kW/m2 at a position 25 mm belowthe center of the heater. The maximum burning speed is determined fromthe chart of a burning heat generation speed thus obtained.

[0093] (4) Compactness (Thickness of a Folded Airbag)

[0094] An airbag 1 (60 liters) for a driver that is prepared by a sewingmethod based on the description in the specification of WO 99/28164 isfolded in the following manner as shown in FIG. 1 (A). An edge a and anedge b are butted against each other on a centerline c-d. The airbag isthen folded in a bellows-like manner to form a sequence of a hill-topfold and a valley bottom fold along lines α, β and γ (at equalintervals), whereby an intermediate folded piece 20 is obtained (seeFIG. 1(B), e, f and g in the figure being folded peripheral edge lines).An edge c and an edge d of the intermediate folded piece 20 are buttedagainst each other on a centerline a-b, and the folded piece is thenfolded in a bellows-like manner to form a sequence of a hill-top foldand a valley bottom fold along lines α′, β′ and γ′ to give a foldedpackage 2 (see FIG. 2), 150 mm×150 mm. In FIG. 7, α′, β′ and γ′designate a hill-top fold and a valley bottom fold in package 2 formedby folding along these lines.

[0095] Next, as shown in FIG. 2, the folded airbag 2 is placed on a flattable 4. A glass plate 3, 300 mm×300 mm, is placed on the airbag, and aload is applied to the airbag with a 1 kg weight 5. The averagethickness X (mm) is measured 30 minutes after applying the load.

[0096] (5) Deployment Test (Observed with a High Speed VTR) and AirbagBurst Evaluation

[0097] An airbag (60 liters) for a driver's seat described in thespecification of WO 99/28164 is prepared by sewing, and an inflator(hybrid type, with a maximum tank pressure of 185 kPa) is attached tothe airbag to give a module. A deployment test is conducted at roomtemperature (n=3).

[0098] The deployment state of the airbag is recorded with a high speedVTR. The airbag observed from the front is deployed. When a distance ofthe periphery from the center reaches 98% or more of the distance of theperiphery in the entire peripheral directions from the center achieved50 msec after starting the deployment, namely, the deployment distance,the deployment is defined to be completed. The time from the start tothe completion of deployment is defined as a deployment time.

[0099] Furthermore, airbags after deployment are observed, and judged tobe burst when even one bag is broken in the deployment test. Whenairbags are burst, the damaged sites are confirmed. When airbags are notburst, the presence of burnt-through-holes is visually confirmed.

[0100] (6) Tensile Strength

[0101] The tensile strength of a silicone coated fabric is measuredaccording to JIS L-1096 8.12.1 (A; strip method).

[0102] (7) Tear Strength

[0103] The tear strength of a silicone coated fabric is measuredaccording to JIS L-1096 6.15.1 (single tongue method).

[0104] (8) Biaxial Tensile Test

[0105] A silicone coated fabric is adjusted to be in a standard stateaccording to JIS L 0105, and a rectangular sample, 270×270 mm, is takentherefrom. The sample is held so that the warp direction and the weftdirection agree with the X direction and the Y direction, respectively,of a tester. Measurements are made on a portion, 200×200 mm, of thesample in the above two directions. A tensile tester (trade name ofBiaxial Tensile Tester 2AT-5000, manufactured by Shimazu Corporation) isused, and the test is conducted by simultaneously elongating biaxicallyat a rate of 200 m/min.

[0106] (9) Observation (SEM) of the Cross Section of a Silicone CoatedFabric and Si Elemental Analysis (SEM/XMA)

[0107] A silicone coated fabric is sectioned along a weaving yarn sothat the resultant cross section includes the center of the yarn to givea cross section where the weaving yarns are most overlapped. Thesilicone coated fabric is attached to a sample table while the fabric isallowed to stand vertically so that the cross section can be observedfrom directly thereabove. The sample is directly observed withoutcoating or spattering. The sample is observed with a scanning electronmicroscope (SEM) (trade name of Scanning Electron Microscope S-3500 N,manufactured by Hitachi Ltd.) at a vacuum degree of 50 Pa and anaccelerated voltage of 20 kV.

[0108] Elemental analysis of Si is carried out with an X-raymicroanalyzer (trade name of EMAX 7000, manufactured by Horiba Limited)attached to the above apparatus; andSi-K_(α is observed, and area integration is conducted) 20 times. Of aweaving structural repeating unit of the weaving yarns in the siliconecoated fabric cross section sample, a region from an overlapped centerof the weaving yarns to 50% of the repeating unit length is used as anintegration region for observation. Integration is carried out in thedirection from the front surface to the back surface of the wovenfabric, and a Si distribution amount (count, Y coordinate) is plottedagainst a distance (X coordinate) in the above direction to give agraph. A maximum peak and to another peak height ratio are determinedfrom the heights of Si peaks.

[0109] (10) Coefficient of Friction (MIU)

[0110] Coefficient of Friction (MIU) Determined by KES

[0111] The coefficient of friction of a sample of a silicone coatedfabric 20 cm wide and 20 cm long is measured under standard conditionsdefined by KES (The Standardization and Analysis of Hand Evaluation, 7.2^(nd) Ed. S. Kawabata, 8. The Textile Machinery Society of Japan, 9.1980).

[0112] A sample fabric is sperially capped on the top the surface of afriction probe defined by KES. Measurements are made by moving the probeon a sample fabric that is horizontally held and the fabric is the samefabric that caps the probe. The sample fabric capped thereon in such amanner that the warp and weft directions of the capped sample agree withthe warp and weft directions of the horizontally held sample,respectively each time a measurement is made. Measurements are made atfive sites within the sample, and the average value is obtained.

[0113] (11) Burning Speed according to FMVSS302

[0114] Measurements are made according to FMVSS302 (horizontal method).

[0115] (12) Air Permeability

[0116] The air permeability is measured according to JIS L-1096 8.27 A(Frazier method).

[0117] (13) Air Permeability at High Pressure

[0118] A high pressure type apparatus is prepared, and measurements aremade according to JIS L-1096 8.27 (Frazier method). Using a flangehaving a pressurizing effective diameter of 52 mm, a silicone coatedfabric sample is attached to the measuring portion with bolts with thesilicone coating side down. Air compressed at a pressure of 300 kPa isintroduced at a stretch from a pressure chamber arranged below thesample through a pressure-regulating valve. Air that passes through thesample is collected in a collecting chamber arranged above the sample,and the permeated amount of air is measured with a rotor meter. Apressure of 300 kPa is applied for 10 sec; the pressure of the pressurechamber is then regulated to 50 kPa, and the chamber is closed. Theholding ratio is obtained by measuring a holding pressure 10 sec afterclosing.

[0119] (14) Damage to Keratin

[0120] Measurements are made according to Japanese Unexamined PatentPublication (Kokai) No. 11-344488. Using the skin friction apparatusdescribed in the patent publication, a silicone coated fabric samplehaving a friction area of 10 mm in diameter is affixed, and a panelistis subjected to a test in which rubbing at a rate of 60 rpm is conducted500 times under a load of 200 g. A change in moisture of the keratin ofskin is evaluated from an electric resistance (μS) with a measuringapparatus described in the same patent publication.

EXAMPLES 11 TO 13 AND COMPARATIVE EXAMPLES 11 TO 12

[0121] Nylon 66 described in Japanese Patent Application No. 2001-050177was melt spun with an extruder type spinning machine. A spin finish oilwas applied to the spun filaments, and the filaments were hot drawn togive nylon yarns each having a predetermined yarn size. The yarns showeda tensile strength of 8.5 cN/dtex and an elongation of 21%, andcontained the applied spin finish oil in an amount of 1.0% by weight.

[0122] The spin finish oil was a hydrocarbon solution containing 30% byweight of a mixture composed of 40 parts of dialkyl thiodipropionate, 30parts of PO/EO alkylpolyether and 30 parts of POE hardened castor oiltrialkylester, and was fed by means of an oiling nozzle.

[0123] When the yarn was to be warped, S1700 (trade name, manufacturedby Goo Chemical Co., Ltd.) was applied to the yarn as a warping oil inan amount of 1.0% by weight using a kiss-roll system so that the warpedyarn had 2.0% by weight of the applied oil in a total amount. Warppreparation such as beaming was conducted, and the yarns were woven onan air-jet loom (AJL) to give a woven fabric.

[0124] The woven fabric was neither scoured nor heat set.

[0125] Next, the woven fabrics were coated with an aqueous siliconecomposition dope in an amount of 3 g/m² as a solid component using a dipcoater, and heat treated for 2 minutes within a drying machine (180/200°C.). The silicone composition dope herein was prepared by stirring amixture of 23.5 parts of an aqueous emulsion of silicone (trade name ofDehesive 38197 VP, manufactured by Wacker-Chemie GmbH, Germany), 3 partsof an organopolysiloxane having at least 3 hydrogen atoms attached to Si(trade name of Cross Linker V20, manufactured by Wacker-Chemie GmbH,Germany), 1.5 parts of an organosilicon compound (trade name of AdhesionPromotor HF 86, manufactured by Wacker-Chemie GmbH, Germany) as asuitable adhesive aid and 74.0 parts of water.

[0126] Using a floating knife coater, the resultant woven fabrics werecoated with a liquid silicone composition in an amount of 10 g/m² as asolid component, and heat treated for 1 minute within a drying machine(180/200° C.) to give coated fabrics. The liquid silicone compositionused herein was a mixture of 98 parts of an addition crosslinking typesilicone composition (trade name of Elastosil LR LR6200A/B (manufacturedby Wacker-Chemie GmbH, Germany) containing a crosslinking agent and anaddition reaction catalyst, 3 parts of a generally used addition typecross linking agent (trade name of Cross Linker W, manufactured byWacker-Chemie GmbH, Germany) that was intended to further add anorganopolysiloxane having at least 3 hydrogen atoms attached to Si and 3parts of an organosilicon compound (trade name of Adhesion Promotor HF86, manufactured by Wacker-Chemie GmbH, Germany) suitable as an adhesiveaid. The edge of the coating knife had a thickness of 0.1 mm. Thecoating amount was adjusted by applying a tension of from 10 to 100kgf/m to the woven fabrics.

[0127] Table 1 shows samples having various yarn sizes and weavingtextures, and the results obtained from airbags prepared from the coatedfabrics thus obtained. TABLE 1 Ex. 11 Ex. 12 Ex. 13 Comp. Ex. 11 Comp.Ex. 12 warp weft warp weft warp weft warp weft warp weft Weaving yarnsize 115 115 155 155 235 235 78 78 350 350 (dtex) Single filament 3.23.2 3.2 3.2 2.9 2.9 3.3 3.3 5.9 5.9 size (dtex) Weave density 107 107 9191 75 75 140 140 60 60 (ends or picks/2.54 cm) Woven yarn size 1230512305 14105 14105 17625 17625 10920 10920 21000 21000 parameter (ends.dtex (or picks)/2.54 cm) METSUKE, basis of 107 121 147 97 173 weight offabric (g/m²) Total amt. of 13 13 13 13 13 coating (g/m²) 3 3 3 3 3(applied dope + thin +10 +10 +10 +10 +10 layer coating) Max. radiation81 101 124 63 138 burning speed (kW/m²) Evaluation of bag No burst Noburst No burst Burst No burst burst Observation of No problem No problemNo problem Break of No problem bag damage base fabric Observation of Notobserved Not observed Not observed — Not observed burnt-through-holeDeployment time 27 28 32 — 37 (msec) Foldability (mm) 21 22 27 20 29

[0128] In Comparative Example 11, the yarn size of the woven fabric wastoo small. Consequently, the coated fabric could not resist the airbagdeployment, and resulted in a break of the coated fabric itself, namely,a break of the base fabric. In Comparative Example 12, the yarn size ofthe woven fabric was too large. Consequently, the desired compact airbagcould not be obtained therefrom, and the deployment time was long. InExamples 11 to 23, the airbags thus obtained were compact, caused noproblem about the deployment, produced no burnt-through-hole, and showeda short deployment time.

EXAMPLES 21 TO 27 AND COMPARATIVE EXAMPLES 31 TO 38

[0129] A silicone coated fabric was prepared in the same manner as inExample 11. Tables 2 to 3 show the results of evaluating the tensilestrength and tear strength. TABLE 2 Ex. 21 Ex. 22 Ex. 23 Ex. 24 warpweft warp weft warp weft warp weft Weaving yarn size (dtex) 115 115 155155 155 155 235 235 Single filament size 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2(dtex/filament) METSUKE, basis of weight of 107 106 121 117 fabric(g/m²) Total amount of coating (g/m²) 13 13 13 13 (Applied dope + thin(3 + 10) (3 + 10) (3 + 10) (3 + 10) layer coating) Max. radiationburning speed 81 89 101 132 (kW/m²) Yarn strength (cN/dtex) 8.5 8.5 8.58.5 8.5 8.5 8.5 8.5 Silicone Applied dope HF-3 HF-3 HF-3 No additioncomposition Parts parts parts additive Thin layer HF: 3parts: HF-3parts:HF-3parts: No addition coating W-3parts W-3parts W-3parts Weave density(ends or 107 107 78 78 91 91 58 58 picks/2.54 cm) Woven yarn sizeparameter 12305 12305 12090 12090 14105 14105 13630 13630 (ends · dtex(or picks)/2.54 cm) Woven fabric strength (N/5 cm) 1935 1950 1860 18902150 2170 2670 2710 Weaving yarn strength (N) 9.2 9.3 12.1 12.3 12.012.1 23.4 23.7 Single tongue tear strength 82 88 136 145 131 139 188 193Single tongue tear strength/ 8.9 9.5 11.2 11.8 10.9 11.5 8.0 8.1 wovenyarn strength Evaluation of bag burst No burst No burst No burst Noburst Observation of bag damage No problem No problem No problem Noproblem Observation of burnt- Not observed Not observed Not observed Notobserved through-hole Deployment time (msec) 27 28 28 32 Folding height(mm) 21 21 22 27 Ex. 25 Ex. 26 Ex. 27 warp weft warp weft warp weftWeaving yarn size (dtex) 235 235 235 235 235 235 Single filament size3.2 3.2 3.2 3.2 2.9 2.9 (dtex/filament) METSUKE, basis of weight of 147128 147 fabric (g/m²) Total amount of coating (g/m²) 13 13 13 (Applieddope + thin (3 + 10) (3 + 10) (3 + 10) layer coating) Max. radiationburning speed 132 102 124 (kW/m²) Yarn strength (cN/dtex) 8.5 8.5 8.58.5 8.5 8.5 Silicone Applied dope HF-3 parts HF-3 parts HF-3 partscomposition Thin layer coating W-3 parts HF-3; W-3 HF-3; W-3 additiveparts parts Weave density (ends or 75 75 64 64 75 75 picks/2.54 cm)Woven yarn size parameter 17625 17625 15040 15040 17625 17625 (ends ·dtex (or picks)/2.54 cm) Woven fabric strength (N/5 cm) 2670 2710 23102330 2680 2690 Weaving yarn strength (N) 18.1 18.4 18.3 18.5 18.2 18.2Single tongue tear strength 165 172 202 208 183 187 Single tongue tearstrength/ 9.1 9.4 11.0 11.2 10.1 10.3 woven yarn strength Evaluation ofbag burst No burst No burst No burst Observation of bag damage Noproblem No problem No problem Observation of burnt- Not observed Notobserved Not observed through-hole Deployment time (msec) 32 32 32Folding height (mm) 27 23 27

[0130] TABLE 3 Comp. Ex. 31 Comp. Ex. 32 Comp. Ex. 33 Comp. Ex. 34 warpweft warp weft warp weft warp weft Weaving yarn size (dtex) 78 78 155155 155 155 155 155 Single filament size 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2(dtex/filament) METSUKE, basis of weight of 97 85 121 85 fabric (g/m²)Total amount of coating (g/m²) 13 0 0 13 (Applied dope + thin (3 + 10)(0 + 0) (0 + 0) (3 + 10) layer coating) Max. radiation burning speed 63108 153 68 (kW/m²) Yarn strength (cN/dtex) 8.5 8.5 8.5 8.5 8.5 8.5 8.58.5 Silicone Applied dope HF-3 parts No additives No additives HF-3parts composition Thin layer HF-3; W-3 No additives No additives HF-3;W-3 additive coating parts parts Weave density (ends or 140 140 60 60 9191 60 60 picks/2.54 cm) Woven yarn size parameter 10920 10920 9300 930014105 14105 9300 9300 (ends · dtex (or picks)/2.54 cm) Woven fabricstrength (N/5 cm) 1718 1725 1440 1460 2180 2230 1430 1440 Weaving yarnstrength (N) 6.2 6.3 12.2 12.4 12.2 12.4 12.1 12.2 Single tongue tearstrength 82 88 83 91 59 64 142 149 Single tongue tear strength/ 13.214.1 6.8 7.4 4.8 5.1 11.7 12.2 woven yarn strength Evaluation of bagburst Burst Burst Burst Burst Observation of bag damage Break of Breakof Break caused Break of base fabric base fabric by burning base fabricthrough Observation of burnt- — — — — through-hole Deployment time(msec) — — — — Folding height (mm) 20 19 22 19 Comp. Ex. 35 Comp. Ex. 36Comp. Ex. 37 Comp. Ex. 38 warp weft warp weft warp weft warp weftWeaving yarn size (dtex) 235 235 235 235 235 235 470 470 Single filamentsize 3.2 3.2 3.2 3.2 3.2 3.2 6.7 6.7 (dtex/filament) METSUKE, basis ofweight of 87 147 87 174 fabric (g/m²) Total amount of coating (g/m²) 0 00 0 (Applied dope + thin (0 + 0) (0 + 0) (0 + 0) (0 + 0) layer coating)Max. radiation burning speed 117 212 63 173 (kW/m²) Yarn strength(cN/dtex) 8.5 8.5 8.5 8.5 8.5 8.5 8.5 8.5 Silicone Applied dope Noadditives No additives HF-3parts HF-3 parts composition Thin layer Noadditives No additives HF-3; W-3 HF-3; W-3 additive coating parts partsWeave density (ends or 41 41 75 75 41 41 45 46 picks/2.54 cm) Woven yarnsize parameter 9635 9635 17625 17625 9635 9635 21150 21120 (ends · dtex(or picks)/2.54 cm) Woven fabric strength (N/5 cm) 1440 1450 2180 21901480 1510 3120 3080 Weaving yarn strength (N) 17.8 18.0 14.8 14.8 18.318.7 35.2 34.0 Single tongue tear strength 176 185 93 98 314 321 210 226Single tongue tear strength/ 9.9 10.3 6.3 5.6 17.1 17.2 6.0 6.6 wovenyarn strength Evaluation of bag burst Burst No burst Burst BurstObservation of bag damage Break of Break at Opening of seam No problembase fabric bolt portion in sewed Observation of burnt- — Observedportion Not observed through-hole Deployment time (msec) — 35 — —Folding height (mm) 20 27 20 32

[0131] Furthermore, as shown in Tables 2 and 3, experiments wereconducted in the following manner. Silicone compositions for dopes to beapplied were prepared by adding or without adding an organosiliconcompound (trade name of Adhesion Promotor HF86, manufactured byWacker-Chemie GmbH, Germany) suitable as an adhesive aid. Moreover,silicone compositions for coatings were prepared by adding or withoutadding an organopolysiloxane (trade name of Cross Linker W, manufacturedby Wacker-Chemie GmbH, Germany) that has at least 3 hydrogen atomsattached to Si, and by adding or without adding an organosiliconcompound (trade name of Adhesion Promotor HF86, manufactured byWacker-Chemie GmbH, Germany) suitable as an adhesive aid.

[0132] The airbags in Comparative Examples 31, 32, 34 and 35 were burstdue to the breaking of the base fabrics due to a small yarn size or asmall weave density. The airbag in Comparative Example 33 was burst, andthe burst was observed to be accompanied by a burnt-through-hole. Theairbag in Comparative Example 36 was not burst. However, a break tookplace in a portion where a bolt had been attached thereto, and theairbag appeared to have been torn off the bolt hole. Accordingly, thesafety of the airbag cannot be maintained. These airbags were burst orbroken for the following reasons. The adhesive aid was not added, andthe organopolysiloxane that contained at least 3 hydrogen atoms attachedto Si and that is in general an addition type crosslinking agent was notadditionally added to the coating. Accordingly, the silicone coatedfabric showed a low tear cohesion ratio, and could not hold a suddenimpact of a tear stress. In Comparative Example 37, the adhesive aid andthe crosslinking agent were additionally added to the siliconecompositions, and the weave density was low. As a result, the tearcohesion ratio became too high, and the state of the burst was asfollows: a hot gas leaked from the sewed portion, and a portion havingbeen melted was observed in the seam portion. Because the yarn size ofthe weaving yarn was large in Comparative Example 38, the airbag was notcompact, and had a long deployment time.

[0133] In Examples 21 to 23, 26 and 27, the adhesion aid and thecrosslinking agent were additionally added to the silicone compositions.The silicone coated fabrics showed a tear cohesion ratio in an excellentregion, and the airbags were deployed without a problem. Although thesilicone composition for the coating in Example 25 contained no adhesiveaid, no problem arose. Although neither the adhesive aid nor thecrosslinking agent was additionally added to the silicone composition inExample 24, the silicone coated fabric showed a relatively low weavedensity and an excellent tear cohesion ratio, and the deployment of theairbag caused no problem.

EXAMPLES 41 TO 43 AND COMPARATIVE EXAMPLES 41 TO 43

[0134] Silicone coated fabrics were prepared in the same manner as inExample 11, and evaluated. The yarn size and weaving texture werealtered, and biaxial tensile tests were carried out. Table 4 shows theresults thus obtained. TABLE 4 Ex. 41 Ex. 42 Ex. 43 Ex. 44 warp weftwarp weft warp weft warp Weft Weaving yarn size (dtex) 115 115 155 155235 235 235 235 Single filament size (dtex) 3.2 3.2 3.2 3.2 2.9 2.9 2.92.9 Yarn strength (cN/dtex) 8.5 8.5 8.5 8.5 8.5 8.5 7.0 7.0 Weavedensity (ends or 107 107 91 91 75 75 75 75 picks/2.54 cm) Woven yarnsize parameter 12305 12305 14105 14105 17625 17625 17625 17625 (dtex ·ends (or picks)/2.54 cm) Biaxial elongation strength of 3830 4020 47904880 6740 6820 5630 5650 Woven fabric (N/20 cm) METSUKE, basis of weightof 107 121 147 147 fabric (g/m²) Total amount of coating (g/m²) 13 13 1313 (Applied dope + thin (3 + 10) (3 + 10) (3 + 10) (3 + 10) layercoating) Max. radiation burning speed 81 101 124 123 (kW/m²) SiliconeApplied dope HF-3 parts HF-3 parts HF-3 parts HF-3 parts compositionThin layer HF 3:W 3 HF 3:W 3 HF 3:W 3 HF 3:W 3 additive coatingEvaluation of bag burst No burst No burst No burst No burst Observationof bag damage No problem No problem No problem No problem Observation ofburnt- Not observed Not observed Not observed Not observed through-holeDeployment time (msec) 27 28 32 32 Folding height (mm) 21 22 27 27 Comp.Ex. 41 Comp. Ex. 42 Comp. Ex. 43 warp weft warp weft warp Weft Weavingyarn size (dtex) 78 78 470 470 940 940 Single filament size (dtex) 3.23.2 6.7 6.7 6.7 6.7 Yarn strength (cN/dtex) 8.5 8.5 8.5 8.5 8.5 8.5Weave density (ends or 140 140 46 46 32 32 picks/2.54 cm) Woven yarnsize parameter 10920 10920 21620 21620 30080 30080 (dtex · ends (orpicks)/2.54 cm) Biaxial elongation strength of 2890 3180 8850 9210 1309014090 Woven fabric (N/20 cm) METSUKE, basis of weight of 2397 177 300fabric (g/m²) Total amount of coating (g/m²) 13 13 13 (Applied dope +thin (3 + 10) (3 + 10) (3 + 10) layer coating) Max. radiation burningspeed 63 173 298 (kW/m²) Silicone Applied dope HF-3 parts HF-3 partsHF-3 parts composition Thin layer HF 3: W 3 HF 3: W 3 HF 3: W 3 additivecoating Evaluation of bag burst Burst No burst No burst Observation ofbag damage Seam opened No problem No problem Observation of burnt- — Notobserved Not observed through-hole Deployment time (msec) — 37 39Folding height (mm) 20 32 45

[0135] The base fabric in Comparative Example 41 showed an insufficientbiaxial elongation strength because the base fabric itself was brokendue to insufficient pressure the resistance. Although the siliconecoated fabrics in Comparative Examples 42 and 43 showed a very highbiaxial elongation strength, and the airbags caused no problem, thedesired compact airbags were not obtained, and the deployment time waslong.

[0136] The silicone coated fabrics in Examples 41 to 43 showed asufficient biaxial elongation strength, and the deployment of airbagscaused no problem. Example 43 is an example wherein the hot drawingratio was decreased during the preparation of a nylon 66 yarn, and as aresult the weaving yarn strength was low. However, the silicone coatedfabric showed a sufficient biaxial elongation strength, and thedeployment of the airbag caused no problem.

EXAMPLES 51 TO 57 AND COMPARATIVE EXAMPLES 51 TO 56

[0137] A silicone coated fabric was prepared in the same manner as inExample 1 except for the following procedure, and evaluated: a nylon 66woven fabric was prepared on a water-jet loom; an acrylate sizing agentwas used in place of a warping finish oil during warping; and alkaliscouring, water washing, drying and heat setting at 70° C. wereconducted to give a gray fabric for a silicone coated fabric. Table 5shows the results thus obtained by changing a yarn size, a weavingtexture and a coating amount. TABLE 5 Ex. 51 Ex. 52 Ex. 53 Ex. 54 warpweft Warp weft warp weft warp Weft Weaving yarn size (dtex) 110 110 155155 155 155 155 155 Single filament size (dtex) 3.2 3.2 2.9 2.9 2.9 2.92.9 2.9 Weave density (ends or 107 107 91 91 91 91 91 91 picks/2.54 cm)Woven yarn size parameter 11770 11770 14105 14105 14105 14105 1410514105 (dtex · ends (or picks)/2.54 cm) METSUKE, basis of weight of 103121 121 121 fabric (g/m²) Total amount of coating (g/m²) 10 5 13 21(Applied dope + thin (3 + 7) (1 + 4) (3 + 10) (3 + 18) layer coating)Max. radiation burning speed 88 129 101 93 (kW/m²) CF* (MIU) of uncoatedsurface 0.10 0.17 0.13 0.19 0.12 0.18 0.12 0.18 CF* (MIU) of coatedsurface 0.11 0.15 0.12 0.13 0.12 0.12 0.13 0.21 Evaluation of bag burstNo burst No burst No burst No burst Observation of bag damage No problemNo problem No problem No problem Observation of burnt- Not observed Notobserved Not observed Not observed through-hole Deployment time (msec)27 29 28 29 Folding height (mm) 21 22 22 22 Ex. 55 Ex. 56 Ex. 57 warpweft warp weft warp weft Weaving yarn size (dtex) 155 155 235 235 235235 Single filament size (dtex) 2.9 2.9 2.9 2.9 2.9 2.9 Weave density(ends or 91 91 75 75 75 75 picks/2.54 cm) Woven yarn size parameter14105 14105 17625 17625 17625 17625 (dtex · ends (or picks)/2.54 cm)METSUKE, basis of weight of 121 147 147 fabric (g/m²) Total amount ofcoating (g/m²) 25 10 25 (Applied dope + thin (3 + 23) (3 + 7) (3 + 23)layer coating) Max. radiation burning speed 86 124 107 (kW/m²) CF* (MIU)of uncoated surface 0.12 0.18 0.13 0.17 0.13 0.17 CF* (MIU) of coatedsurface 0.15 0.25 0.12 0.20 0.18 0.28 Evaluation of bag burst No burstNo burst No burst Observation of bag damage No problem No problem Noproblem Observation of burnt- Not observed Not observed Not observedthrough-hole Deployment time (msec) 30 31 33 Folding height (mm) 23 2323

[0138] TABLE 5-2 Comp. Ex. 51 Comp. Ex. 52 Comp. Ex. 53 Comp. Ex. 54Comp. Ex. 55 Comp. Ex. 56 warp weft warp weft warp weft warp Weft warpweft warp weft Weaving yarn size (dtex) 78 78 155 155 235 235 350 350350 350 155 155 Single filament size (dtex) 3.3 3.3 2.9 2.9 2.9 2.9 5.95.9 5.9 5.9 2.9 2.9 Weave density (ends or 140 140 91 91 75 75 60 60 6060 91 91 picks/2.54 cm) Woven yarn size parameter 10920 10920 1410514105 17625 17625 21000 21000 21000 21000 14105 14105 (dtex · ends (orpicks)/2.54 cm) METSUKE, basis of weight of 97 121 147 173 173 121fabric (g/m²) Total amount of coating (g/m²) 30 30 30 10 30 0 (Applieddope + thin (3 + 27) (30 + 27) (30 + 27) (3 + 7) (3 + 27) (0 + 0) layercoating) Max. radiation burning speed 49 82 101 178 151 153 (kW/m²) CF*(MIU) of uncoated surface 0.10 0.17 0.12 0.18 0.13 0.17 0.17 0.20 0.170.20 0.17 0.25 CF* (MIU) of coated surface 0.39 0.45 0.32 0.40 0.31 0.390.10 0.20 0.40 0.43 — — Evaluation of bag burst Burst No burst No burstNo burst No burst Burst Observation of bag damage Break of No problem Noproblem No problem No problem Burn-through base fabric break Observationof burnt- — Not observed Not observed Not observed Not observed —through-hole Deployment time (msec) — 34 36 37 39 — Folding height (mm)19 23 23 29 30 22

[0139] In Comparative Examples 51, 52, 53 and 55 in which the siliconecoated fabrics each had a large coating amount, the coated fabricsshowed a glossy coating surface, a poor unevenness and a highcoefficient of friction, and gave a tacky touch. The airbags preparedfrom the silicone coated fabrics each showed a long deployment time.Although the total yarn size of the weaving yarn in Comparative Example54 was large, and the coefficient of friction was decreased, the airbagwas not compact.

[0140] In Comparative Example 56 in which the fabric had no siliconecoating, the airbag was burst in a bag burst test. The fabric showed acoefficient of friction (MIU) of 0.17 in the warp direction and 0.25 inthe weft direction. The coefficients of friction were slightly highcompared with those of silicone coated fabrics on the uncoated surface(back side) in Examples 52 to 55. Moreover, it was found that the degreeof damage to the skin of a human body caused by the contact of each ofthe fabrics with the skin was as large as from 62 to 70 μS when thedegree of contact damage was evaluated for damage to the keratin.

[0141] In Examples 51 to 57, the silicone coated fabrics each showed adecreased coefficient of friction not only on the coating surface butalso on the uncoated surface that was the back side of the coatedsurface, and the airbags each showed a shortened deployment time.Moreover, the damage to keratin of the coated fabrics was evaluated tobe as low as 3.8 μS and 4.2 μS on the coating surface and on theuncoated surface (back side), respectively. It was found that even whena fabric had no silicone coating layer, a silicone dip significantlysuppressed damage to the skin. In Comparative Example 54, the siliconecoated fabric had too large a yarn size, and a low coefficient offriction; however, a desired compact airbag was not prepared, and theairbag showed a long deployment time.

EXAMPLES 61 TO 62 AND COMPARATIVE EXAMPLES 61 TO 62

[0142] Silicone coated fabrics were prepared and evaluated in the samemanner as in Example 11 except that a nylon 66 woven fabric was preparedwith a rapier loom. Table 6 shows the evaluation results of the airpermeability of silicone coated fabrics wherein a coating amount and anapplication procedure were varied. TABLE 6 Ex. 61 Ex. 62 Comp. Ex. 61Comp. Ex. 62 warp weft warp weft Warp weft warp weft Weaving yarn size(dtex) 155 155 155 155 155 155 155 155 Single filament size (dtex) 2.92.9 2.9 2.9 2.9 2.9 2.9 2.9 Weave density (ends or 91 91 91 91 91 91 9191 picks/2.54 cm) Woven yarn size parameter 14105 14105 14105 1410514105 14105 14105 14105 (dtex · ends (or picks)/2.54 cm) METSUKE, basisof weight of 121 121 121 121 fabric (g/m²) Total amount of coating(g/m²) 13 18 3 4 (Applied dope + thin (3 + 10) (3 + 15) (3 + 0) (0 + 4)layer coating) Max. radiation burning speed 101 84 171 143 (kW/m²)Frazier air permeability ≦0.1 ≦0.1 ≦0.1 ≦0.1 (cm³/cm²/sec) High pressureair permeability ≦1 ≦1 50 2 at 300 kPa (cm³/cm²/sec) Evaluation of bagburst No burst No burst No burst No burst Observation of bag damage Noproblem No problem No problem No problem Observation of burnt- Notobserved Not observed Observed Observed through-hole Deployment time(msec) 28 29 33 30 Maintainability of high ≧90% ≧90% ≦50% 80-90%pressure (300 kPa*10 sec → 50 kPa*10 sec)

[0143] The silicone coated fabrics in Examples 61 to 62 showed airimpermeability the level of which cannot be measured by Frazier methodbecause the indication air permeability under differential pressure wasbelow the lowerest readable limit of reading of Frazier method).Moreover, the coated fabrics showed a pressure maintainability of 90% ormore when the airbags were once held at a pressure as high as 300 kPafor 10 sec and then held at a pressure of 50 kPa for 10 sec.

[0144] On the other hand, in Comparative Example 61, a base woven fabricwas dip coated with a dope alone in an amount of 3 g/m². Although thecoated fabric showed air impermeability by Frazier method, it showed airpermeability under high pressure. Moreover, the airbag showed a longdeployment time. The silicone coated fabric in Comparative Example 62had only a thin layer coating in an amount of 4 g/m². Although thecoated fabric showed slight air permeability under high pressure, itcould not maintain a pressure after applying a high pressure.

EXAMPLES 71 TO 74 AND COMPARATIVE EXAMPLES 71 TO 75

[0145] Silicone coated fabrics were prepared and evaluated in the samemanner as in Examples 11. A coating amount, a coating procedure and acoating composition were varied, and the results were compared. Table 7shows the results thus obtained. Two parts of a coloring agent (tradename of Elastosil Pigment Pastes FL Red, manufactured by Wacker-ChemieGmbH, Germany) was further added to each of the coatings in order todistinguish between the front and back sides. TABLE 7 Ex. 71 Ex. 72 Ex.73 Ex. 74 Comp. Ex. 71 warp weft Warp weft warp weft warp weft warp weftWeaving yarn size 175 175 175 175 175 175 175 175 175 175 (dtex) Singlefilament size 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 (dtex) Weavedensity 83 83 83 83 83 83 83 83 83 83 (ends picks/2.54 cm) Woven yarnsize 14525 14525 14525 14525 14525 14525 14525 14525 14525 14525parameter (dtex · ends (or picks)/ 2.54 cm) METSUKE, basis of weight of124 124 124 124 124 fabric (g/m²⁾ Total amount 7 9 13 18 3 of coating(g/m²) (3 + 4) (3 + 6) (3 + 10) (7 + 11) (3 + 0) (Applied dope + thinlayer coating) Max. radiation burning speed 136 129 113 102 198 (kW/m²)Silicone Applied HF-3 parts HF-3 parts HF-3 parts HF-3 parts HF-3 partscomposition dope additive Thin HF 3: W 3 HF 3: W 3 HF 3: W 3 HF 3: W 3HF 3: W 3 layer parts parts parts parts parts coating Evaluation of bagburst No burst No burst No burst No burst No burst Observation of bagdamage No problem No problem No problem No problem No problemObservation Not observed Not observed Not observed Not observed Observedof burnt- through-hole Deployment 28 29 29 30 33 time (msec) FMVSSburning Self- Self- Self- Self- 120 speed (mm/min) extinguishingextinguishing extinguishing extinguishing Burned 43 39 35 25 254distance (mm) Burning 40 37 29 23 127 time (sec) Comp. Ex. 72 Comp. Ex.73 Comp. Ex. 74 Comp. Ex. 75 warp weft warp weft warp weft warp weftWeaving yarn size 175 175 175 175 175 175 175 175 (dtex) Single filamentsize 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 (dtex) Weave density 83 83 83 83 8383 83 83 (ends or picks/2.54 cm) Woven yarn size 14525 14525 14525 1452514525 14525 14525 14525 parameter (dtex · ends (or picks)/2.54 cm)METSUKE, basis of 124 124 124 124 weight of fabric (g/m²) Total amountof coating 4 30 7 10 (g/m²) (0 + 4) (0 + 30) (0 + 7) (3 + 7) (Applieddope + thin Dip in modified layer coating) silicone Max. radiation 16591 155 161 burning speed (kW/m²) Silicone Applied HF-3 parts HF-3 partsHF-3 parts No additive composition dope additive Thin HF 3: W 3 HF 3: W3 HF 3: W 3 HF 3: W 3 parts layer parts parts parts coating Evaluationof bag burst No burst No burst No burst No burst Observation No problemNo problem No problem No problem of bag damage Observation of burnt-Observed Not observed Observed Observed through-hole Deployment time(msec) 32 34 29 29 FMVSS burning speed 154 Self- 131 148 (mm/min)extinguishing Burned distance (mm) 254 27 254 254 Burning 99 21 116 103time (sec)

[0146] The deployment time was shortened, and formation of aburnt-through-hole was suppressed in any of Examples 71 to 74 in which awoven fabric was coated with two types of silicones. A base woven fabricwas coated with one type of silicone by dip coating alone in ComparativeExample 71. A base woven fabric was coated with one type of silicone byknife coating alone in Comparative Example 71. The coating amount ofeach of the silicone coated fabrics was small, and both coated fabricsdid not pass the FMVSS 302 burning evaluation. The coating amount wasexcessive in Comparative Example 73, and the deployment time wasextended. A base woven fabric was coated with one type of silicone byknife coating alone in Comparative Example 74. The silicone coatedfabric was unacceptable in burning inhibition effect, and aburnt-through-hole was observed on the base woven fabric. A base wovenfabric was coated with a modified silicone that is used as aflexibilizer by dip coating in Comparative Example 75. The modifiedsilicone was an amino-modified one (trade name of CT 95E, manufacturedby Wacker-Chemie GmbH, Germany). The silicone coated fabric wasinsufficient for a burning inhibition effect, and did not pass the FMVSS302 burning test. Moreover, a burnt-through-hole was observed.

[0147]FIG. 5 is a scanning electron microscope (SEM) photographperspectively photographed so that a cross section and the coatingsurface of a cross-sectional sample of the silicone coated fabric inExample 73 could be observed. The following is understood from FIG. 5:first, there is no open pores between a warp and a weft, and filaments(a warp or weft) spread over other filaments (a weft or warp)overlapping intersected woven yarn whereby covering the woven yarnbeneath (the weft or warp yarn) (the weft or warp), and as a result, thewarps and wefts are densely gathered to form a dense woven fabric; next,the silicone coating surface has a recessed and protruded shape thatappears to have traced the ridges of the weaving yarns of the wovenfabric; moreover, the silicone coating is very thin and uniform;furthermore, dip coating of silicone is not substantially found amongyarns by SEM observation.

[0148] In order to carry out elemental analysis of Si of the silicone ina silicone coated fabric, the sample in Example 73 was sectioned along aweaving yarn so that the resultant cross section includes the lengthwise center line of the woven yarn width, Si—K_(α) analysis was carriedout with an XMA. FIG. 4 shows the chart. The Si distribution shows amaximum peak in the coating layer portion, and a small peak is observedon the back surface of the coating. The ratio of the small peak to themaximum peak is 0.44 that corresponds to a segregated portion of a dipcoating.

[0149] Similarly, FIG. 3 shows a scanning electron microscope (SEM)photograph and a chart of XMA elemental analysis of the sample inComparative Example 74. The sample had a coating layer alone. A singlepeak of the Si distribution of a silicone coating layer portion alonewas observed.

Industrial Applicability

[0150] The present invention provides a soft and light silicone coatedfabric prepared by coating a highly dense base woven fabric formed froma synthetic fiber having a small yarn size to form a specific texture.The coated fabric particularly shows striking effects of improvingburning resistance (passing the FMVSS burning test), heat resistance,flexibility and a low coefficient of friction. A light and compactairbag that suppresses a burst starting from a burnt-through-hole, andthat shortens a deployment time can be manufactured from the siliconecoated fabric of the present invention.

1. A silicone coated fabric comprising a base woven fabric that isformed from a synthetic fiber weaving yarn having a yarn size of from100 to 270 dtex, and a woven yarn size parameter expressed by a productcalculated by multiplying the yarn size of a weaving yarn and a weavedensity (ends or picks/2.54 cm) of from 10,000 to 25,000 (dtex•ends (orpicks)/2.54 cm) in both the warp direction and the weft direction, asilicone being applied to the woven fabric in an amount of from 5 to 25g/m², and showing a maximum burning speed of from 70 to 150 kW/m2 in aradiation burning test using a cone calorimeter.
 2. The silicone coatedfabric according to claim 1, wherein the ratio of a tear strength to aweaving yarn strength according to the single tongue method is from 8 to15 in both the warp direction and the weft direction.
 3. The siliconecoated fabric according to claim 1 or 2, wherein the biaxial tensilebreaking strength is from 4,000 to 8,000 N/20 cm in both the warpdirection and the weft direction.
 4. The silicone coated fabricaccording to any one of claims 1 to 3, wherein in observation by SEM ofa cross section of the silicon coated fabric, the Si elementdistribution determined by SEM/XMA has a maximum peak and other peakshowing a count having from {fraction (1/20)} to ⅔ of the peak count ina central 50% portion of a site where a warp and a weft are overlappedby weaving from the front and back sides
 5. The silicone coated fabricaccording to any one of claims 1 to 4, wherein the coefficient offriction (MIU) measured according to KES in both the warp direction andthe weft direction is from 0.05 to 0.3 on both the front and back sidesof the fabric.
 6. The silicone coated fabric according to any one ofclaims 1 to 5, wherein the air permeation under a pressure of 300 kPa is1.0 cm³/cm²/sec or less.
 7. The silicone coated fabric according to anyone of claims 1 to 6, wherein the fabric shows the following results ina FMVSS 302 burning test: a) the fire goes out within 60 sec of aburning time with a burning distance of 50 mm or less; or b) the fireburns at a burning speed of 80 mm/min or less at a burnt distance (themaximum distance being 254 mm).
 8. The silicone coated fabric accordingto any one of claims 1 to 7, wherein the synthetic fiber weaving yarn ismainly formed from a poly(hexamethylene adipamide), and the singlefilament size of the weaving yarn is from 0.5 to 4.5 dtex per filament.9. A method of producing a silicone coated fabric, which comprisescoating a woven fabric that is formed from a synthetic fiber weavingyarn having a yarn size of from 100 to 270 dtex, a woven yarn sizeparameter determined by a product calculated by multiplying the yarnsize and a weave density (ends or picks/2.54 cm) of from 10,000 to25,000 (dtex•ends (or picks)/2.54 cm) with silicone in an amount of from5 to 25 g/m² by a combination of the two types of applications mentionedin (1) and (2) below, and crosslinking the silicone coating: (1)applying to the woven fabric a dope composed of a silicone compositionin an amount of from 1 to 21 g/m² as a solid component; and (2) coatingthe woven fabric with a liquid silicone composition in an amount of from4 to 24 g/m².
 10. An airbag comprising the silicone coated fabricaccording to any one of claims 1 to
 8. 11. An airbag comprising thesilicone coated fabric produced by the production method according toclaim 9.